1. Field of the Invention
The present invention relates to an apparatus and method for dividing and combining electromagnetic energy. In particular, the present invention relates to an apparatus and method for dividing, amplifying and combining a high power microwave source using a wide-angle lens.
2. Description of Related Art
Satellite communication systems require high levels of microwave energy to provide for high data rates and error free reception of signals. Traditionally, equipment capable of providing such high energy levels of microwave power is very expensive, requires excessive amounts of power and compartment space, and has a short service life. Moreover, these problems are aggravated as the output power levels are increased.
The prior art: has attempted to resolve these shortcomings and provide high energy microwave signals using solid state power devices. To provide the high power required in satellite communications, the prior art has attempted to combine several solid state devices to cause their power output to be combined, because solid state power devices are inherently low power. The summing of individual energy levels simulates a single higher level energy source.
U.S. Pat. No. 4,835,496, issued to Schellenberg et al., discloses a power divider/combiner circuit fabricated in a planar integrated circuit. The source signal is divided, each of the divided signals is amplified, and the amplified signals are recombined. The device uses a microstrip line that branches out into high impedance lines. The lines are converted using a step transformer and isolation resistors placed between lines to dampen unwanted modes. With the device of Schellenberg, equal amplitude and phase are difficult to obtain in dividing and combining the microwave signal. Therefore, the device of Schellenberg is not fully successful in combining the individual small power sources into a single higher level energy source.
U.S. Pat. No. 4,588,962, issued to Saito et al., discloses a waveguide power divider/combiner that uses a dielectric lens for making the phase and magnitude of the microwave signal uniform. The device of Saito uses a waveguide and a sectoral horn to distribute the electromagnetic energy. The energy is then coupled to microstrip line by means of electromagnetic induction. The device of Saito requires the careful design of electromagnetic coupling mechanisms to the microstrip, which makes the divider/combiner of Saito very complex and difficult to manufacture. The device of Saito also requires the machining, cutting and positioning of hard metallic materials such as brass and aluminum that further increase the fabrication time and costs. F Several techniques are also disclosed in U.S. Pat. Nos. 4,129,839 issued to Galani, et al.; 4,386,324 issued to Schellenberg; 4,450,418 issued to Yu; and 4,639,694 issued to Seino, et al. Additional techniques of power combining are disclosed in W. Rotman, et al., "Wide-Angle Microwave Lens for Line Source Applications," IEEE Transactions on Antennas and Propagation, November 1963, pp. 623-632; M. D. Abouzahra, et al., "Use of Circular Sector Shaped Planar Circuits for Multiport Power Divider-Combiner Circuits," IEEE MTT-S Digest, 1988, pp. 661-664; E. Belohoubek, et al., "30-Way Radial Power Combiner for Miniature GaAs FET Power Amplifiers," IEEE MTT-S Digest, 1986, pp. 515-518; E. J. Wilkinson, "An N-Way Hybrid Power Divider," IRE Transactions on Microwave Theory and Techniques, January 1960, pp. 116-118; and D. Staiman, et al., "New Technique for Combining Solid-State Sources," IEEE Journal of Solid-State Circuits, Vol.SC-3, No. 3, September 1968, pp. 238-243.
While the prior art provides several methods and devices for power combining, these methods are inefficient due to coupling losses. The inefficiencies in power combining also limit the number of devices that may be combined and make them unsuitable for combining large numbers of devices. Additionally, the prior art devices offer limited power amplification abilities, have excessive coupling between elements and are expensive to fabricate.
Thus, there is a need for an apparatus and method that provides efficient microwave power dividing and combining at low cost.